In joining pipes together, a possible alternative is to form perpendicular flanges at the ends of the pipes to be joined, which are then coupled together. In the case of pipes that can be plastically worked up, the flange can be formed by suitably shaping the pipe end. However, if the pipe diameter and the thickness of the pipe wall is large, a considerable force is needed for the shaping operation. Forming a collar on a pipe with a diameter of 200-400 mm requires a force of several thousand kilopond. In this case, the bearing elements transmitting the force constitute an important part of the functional whole.
In a previously known solution (patent application FI A 870799), a collar at an angle of 35.degree.-40.degree. is first formed at the pipe end, then the forming cone is replaced or an auxiliary forming head is mounted on it, whereupon a final rectangular collar is formed. The cone is held in a chuck by its shaft, the chuck being rotatably mounted on the frame. In another known device, the forming cone can be mounted at different positions in the chuck to permit the formation of collars on pipes of different sizes. In the known solutions, the forming cone must be fitted anew between the first and second stages of the operation, and the cone is only supported by one end. Moreover, a separate fit is needed for each pipe size.